1. Technical Field
The present invention relates to a paper output unit for an ink-jet printer, and more particularly, relates to a paper jam-free output apparatus for an inkjet printer for preventing paper jams that may occur due to the reverse rotation of a paper drive mechanism which feeds the next paper when the current paper on which printing is completed has not been output yet to a top output tray.
2. Related Art
Conventional ink-jet printers typically include a paper feeding unit for feeding each individual sheet of paper into the printer, a paper conveyance unit for conveying or transport each sheet of paper fed from the paper feeding unit through a print zone for printing, a print unit for printing images on the sheet of paper as the sheet of paper is transported through the print zone during a print cycle, and a paper output unit for delivering the sheet of paper on which printing is completed through the print unit to an output tray generally placed outside of the printer. Exemplary configurations of such an ink-jet printer are disclosed in U.S. Pat. No. 5,595,380 for Sheet Media Handling System For Aligned Insertion Of Single Sheet Medium issued to McCue, Jr. et al., U.S. Pat. No. 5,291,227 for Ink Jet Printer Having Improved Paper Transport Mechanism issued to Suzuki, U.S. Pat. No. 5,216,442 for Moving Platen Architecture For An Ink Jet Printer issued to Parks et al., U.S. Pat. No. 5,152,622 for Printer With Improved Anti-Skew Mechanisms issued to Rasmussen et al., and U.S. Pat. No. 5,121,139 for Compact Ink Jet Printer Having A Drum Drive Mechanism issued to Burke.
Generally, each sheet of paper is delivered to the paper transport unit from the paper feeding unit. A paper feed roller first rotates in a reversed, clockwise direction so as to align the sheet of paper for proper conveyance through the print zone for printing. When the sheet of paper is aligned for proper conveyance, the paper feed roller then rotates in a forward, counter-clockwise direction so as to convey the sheet of paper through the print zone for printing. As the paper is being printed, a delivery roller of the paper output unit rotates to deliver the paper to the output tray. Simultaneous to the delivery of the printed paper, the paper feed roller also reverses its rotation so as to align a next sheet of paper for printing. As the paper feed roller begins to rotate in a reversed, clockwise direction, however, the tail end of paper as output by the paper output unit is often held back between the delivery roller and the friction star wheel, thus resulting in a paper jam.
One solution to this problem as I have recently observed is to install a paper output hook assembly having a delivery hook and gear in which the delivery hook is used to rotate in a paper output direction for pulling the paper that has been lightly caught between the delivery roller and the friction star wheel for complete delivery when the paper feed roller begins to rotate in a reversed, clockwise direction. However, this solution requires an especially constructed driving mechanism for the paper output hook assembly, and consumes valuable time for paper delivery which causes time delay and creates noise due to the operation of the paper output hook assembly. Moreover, a separate gear for operating the delivery hook and other complex parts and motors are necessarily required which increases the production costs and decreases the production yield.